Various factors of womanhood predict increased risk of breast cancer, e.g., early menarche, late first childbirth, low parity, late menopause, obesity, and family history of this disease. The independence and interaction of these factors in relationship to breast cancer risk, however, particularly over a lifetime, have not been explored adequately. We propose to identify combinations of 1) catamenial, contraceptive, and reproductive experiences; 2) physical, physiological, and social factors; and 3) exogenous hormone usages that affect the lifetime risk of developing breast cancer. These experiences and factors have been collected and partially encoded for statistical analyses of approximately 2,000 white breast cancer patients and 4,000 noncancer control subjects from the San Francisco Bay Area, 1970-1977. We plan to combine relative risks estimated for these experiences and factors with breast cancer incidence rates from the same area (San Francisco-Oakland metropolitan area--NCI-SEER) into an algorithm for estimating lifetime breast cancer risk for white U.S women with specified configurations of risk factors. The algorithm will permit development of a hand-scored breast cancer risk appraisal instrument, which will be validated using independent data sets of risk factors among breast cancer patients and control subjects. The rationale for determining the independence and interaction of selected factors as predictors of lifetime risk of breast cancer relates to opportunities for effective prevention and control of this disease in future generations. These estimates of lifetime risk will facilitate physician assessment and guidance, and will provide basic data for public health educational programs.